Equine Squamous Cell Carcinoma Study Guide

Overview and Clinical Importance

Squamous cell carcinoma (SCC) is the second most common tumor in horses after equine sarcoid and the most common malignant skin tumor in the species. SCC arises from squamous epithelial cells that form the outermost layer of skin and line mucous membranes. This neoplasm predominantly affects non-pigmented skin areas exposed to ultraviolet radiation and is especially concerning because of its locally invasive nature and potential for metastasis if left untreated.

Understanding equine SCC is crucial for the NAVLE as questions frequently address risk factors, anatomic predilection sites, breed susceptibility, diagnostic approaches, and treatment options. Early recognition and intervention significantly improve prognosis.

Etiology and Pathogenesis

Risk Factors

Ultraviolet (UV) Radiation: Chronic UV exposure is the primary carcinogen for cutaneous and ocular SCC. UV light induces DNA damage in keratinocytes, particularly affecting the tumor suppressor gene p53. Non-pigmented skin lacks melanin protection, making these areas highly susceptible.